1. Field
The present disclosure relates to an electric motor control system.
2. Description of the Related Art
In general, control systems that control an electric motor mounted in a hybrid vehicle or an electric vehicle include an inverter disposed between a direct current (DC) power source and the electric motor.
As is widely known, the inverter includes a plurality of switching elements each formed from a semiconductor switching element, such as a transistor. By performing on/off control on each of the switching elements of the inverter, DC power input from the DC power source to the inverter is converted into an alternating current (AC) power, which is supplied to the electric motor. Alternatively, power (AC power) generated and output by a regenerative operation performed by the electric motor is converted into DC power and is charged into an electricity storage device (e.g., a secondary battery) disposed on the DC power source side.
In addition, as described in, for example, Japanese Unexamined Patent Application Publication Nos. 2007-143293 and 2008-167616, among control systems of such a type, some systems have a protection function for protecting the switching elements of the inverter from an applied voltage that exceeds the withstand voltage of the switching elements.
Japanese Unexamined Patent Application Publication Nos. 2007-143293 and 2008-167616 describe a technique for variably controlling a power source voltage input to the inverter using a converter in accordance with a detected temperature of the switching elements while taking into account that the withstanding voltage of the switching elements decreases with decreasing temperature of the switching elements.